Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57.
Scoliosis is a general term for the sideways (lateral) curving of the spine, usually in the thoracic or thoracolumbar region. Scoliosis is commonly broken up into different treatment groups, Adolescent Idiopathic Scoliosis, Early Onset Scoliosis and Adult Scoliosis.
Adolescent Idiopathic Scoliosis (AIS) typically affects children between ages 10 and 16, and becomes most severe during growth spurts that occur as the body is developing. One to two percent of children between ages 10 and 16 have some amount of scoliosis. Of every 1000 children, two to five develop curves that are serious enough to require treatment. The degree of scoliosis is typically described by the Cobb angle, which is determined, usually from x-ray images, by taking the most tilted vertebrae above and below the apex of the curved portion and measuring the angle between intersecting lines drawn perpendicular to the top of the top vertebrae and the bottom of the bottom. The term idiopathic refers to the fact that the exact cause of this curvature is unknown. Some have speculated that scoliosis occurs when, during rapid growth phases, the ligamentum flavum of the spine is too tight and hinders symmetric growth of the spine. For example, as the anterior portion of the spine elongates faster than the posterior portion, the thoracic spine begins to straighten, until it curves laterally, often with an accompanying rotation. In more severe cases, this rotation may actually create a noticeable deformity, wherein one shoulder is lower than the other. Currently, many school districts perform external visual assessment of spines, for example in all fifth grade students. For those students in whom an “S” shape or “C” shape is identified, instead of an “I” shape, a recommendation is given to have the spine examined by a physician, and commonly followed-up with periodic spinal x-rays.
Typically, patients with a Cobb angle of 20° or less are not treated, but are continually monitored, often with subsequent x-rays. Patients with a Cobb angle of 40° or greater are frequently candidates for fusion surgery. It should be noted that many patients do not receive such a spinal assessment, for numerous possible reasons. Many school districts do not perform this simple assessment, and many children do not regularly visit a physician. Therefore, the curve often progresses rapidly and severely. There is a large population of grown adults with untreated scoliosis, some having extreme cases exhibiting Cobb angles of 90° or greater. Many adults having untreated scoliosis, though, do not have pain associated with their deformity and live relatively normal lives, though oftentimes with restricted mobility and motion. In AIS, the ratio of females to males having Cobb angles under 10° is about one to one. However, at Cobb angles above 30°, females outnumber males by as much as eight to one. Fusion surgery can be performed on the AIS patients or on adult scoliosis patients. In a typical posterior fusion surgery, an incision is made down the length of the back and Titanium or stainless steel straightening rods are placed along the curved portion. These rods are typically secured to the vertebral bodies, for example with hooks or bone screws, or more specifically pedicle screws, in a manner that allows the spine to be straightened. Usually, at the section selected for fusion, the intervertebral disks are removed and bone graft material is placed to create the fusion. If autologous graft material is used, the bone is generally harvested from a hip via a separate incision.
Alternatively, fusion surgery may be performed anteriorly. A lateral and anterior incision is made for access. Usually, one of the lungs is deflated in order to allow access to the spine from this anterior approach. In a less-invasive version of the anterior procedure, instead of the single long incision, approximately five incisions, each about three to four cm long are made in several of the intercostal spaces (between the ribs) on one side of the patient. In one version of this minimally invasive surgery, tethers and bone screws are placed and secured to the vertebra on the anterior convex portion of the curve. Currently, clinical trials are being performed in which staples are used instead of the tether/screw combination. One advantage of this surgery in comparison with the posterior approach is that scars resulting from the several smaller incisions are not as dramatic, though they are still located in a visible area, when a bathing suit, for example, is worn. Staple-based techniques have experienced some difficulty in clinical trials. The staples tend to pull out of the bone when a critical stress level is reached.
In some cases, after surgery, the patient will wear a protective brace for a few months as the fusing process occurs. Once the patient reaches spinal maturity, it may be difficult to remove the rods and associated hardware in a subsequent surgery because the fusion of the vertebra usually incorporates the rods themselves. Therefore, standard practice is to leave this implant in for life. With either of these two surgical methods, after fusion the patient's spine is rendered straight, but, depending on the number of vertebrae that were fused, limitations in the degree of flexibility, both in bending and twisting, are often observed. As fused patients mature, the fused section of the spine can impart significant stresses on the adjacent non-fused vertebrae, and often, other problems including pain can occur in these areas, sometimes necessitating further surgery. This tends to be in the lumbar portion of the spine that is prone to problems in aging patients. Many physicians are now interested in fusionless surgery for scoliosis, which may be able to eliminate, or at least reduce, one or more of the drawbacks of fusion.
One group of patients in which the spine is especially dynamic is the subset known as Early Onset Scoliosis (EOS), which typically occurs in children before the age of five, and more often in boys than in girls. EOS is a more rare condition than AIS, occurring in only about one or two out of 10,000 children, but can be severe, sometimes affecting the normal development of organs. Because the spines of these children will generally grow a large amount after treatment, non-fusion distraction devices known as growing rods and a device known as the VEPTR—Vertical Expandable Prosthetic Titanium Rib (“Titanium Rib”) have been developed. These devices are typically adjusted approximately every six months, or as required to match the child's growth, until the child is at least eight years old, and sometimes until they are 15 years old. Each adjustment requires a surgical incision to access the adjustable portion of the device. Because the patients may receive the device at an age as early as six months old, this treatment may require a large number of surgeries. Because of the multiple surgeries, these patients have a rather high incidence of infection.
Returning to the AIS patients, the treatment methodology for those with a Cobb angle between 20° and 40° is quite controversial. Many physicians prescribe a brace (for example, the Boston Brace) for a patient to wear on his body, under the clothes, 18 to 23 hours a day until the patient become skeletally mature (e.g., age 16). Because these patients are all passing through their socially demanding adolescent years, it is a quite serious prospect to choose between wearing a somewhat bulky brace that covers most of the upper body, having fusion surgery that may leave large scars and limit motion, and doing nothing and risking becoming disfigured and possibly disabled. It is common knowledge that many patients have, at times, hidden their braces, for example, in a bush outside of school, in order to escape embarrassment associated with the brace(s). The patient compliance with brace wearing has been so problematic that special braces have been constructed that sense the body of the patient and keep track of the amount of time per day that the brace is worn. Even such special braces have problems with patient compliance: patients have been known to place objects into unworn braces of this type in order to fool the sensor. Coupled with the inconsistent patient compliance with brace usage, is a feeling by many physicians that braces, even if used properly, are not at all effective at curing scoliosis. Physicians may agree that bracing can possibly slow down or even temporarily arrest curve (Cobb angle) progression, but they have noted that as soon as the treatment period ends and the brace is no longer worn, often the scoliosis progresses rapidly to a Cobb angle even more severe than it was at the beginning of treatment. Some say the reason for the supposed ineffectiveness of the brace is that it braces only on a portion of the torso, and not on the entire spine. Currently a prospective, randomized, 500-patient, clinical trial known as BrAIST (Bracing in Adolescent Idiopathic Scoliosis Trial) is enrolling patients, 50% of whom will be treated with the brace and 50% of who will simply be watched. Cobb angle data from these patients will be measured continually up until they reach skeletal maturity, or until a Cobb angle of 50° is reached, at which time the patient will likely undergo surgery. Many physicians feel that the BrAIST trial will show that braces are completely ineffective. If this is the case, the quandary about what to do with AIS patients who have a Cobb angle of between 20° and 40° will only become more pronounced. It should be noted that the patient population having a Cobb angle of 20-40° is as much as ten times larger than the population having a Cobb angle of 40° and greater.
Distraction osteogenesis, also known as distraction callotasis and osteodistraction has been used successfully to lengthen various bones of the body (e.g., long bones). Typically, the bone, if not already fractured, is purposely fractured by means of a corticotomy, and the resulting two segments of bone are gradually distracted apart, thereby allowing new bone to form in the gap. If the distraction rate is too high, there is a risk of nonunion. If the rate is too low, there is a risk that the two segments will prematurely, fuse to each other more than desired before the distraction period is complete. Once the desired length of the bone is achieved using this process, the bone is allowed to consolidate. Distraction osteogenesis applications are mainly focused on the growth of the femur or tibia, but may also include the humerus, the jaw bone (micrognathia), or other bones. There are many reasons for lengthening or growing bones which may be desirable. The applications including, but not limited to: post osteosarcoma bone cancer, cosmetic lengthening (both legs-femur and/or tibia) in short stature or dwarfism/achondroplasia; lengthening of one limb to match the other (congenital, post-trauma, post-skeletal disorder, prosthetic knee joint), nonunions.
Distraction osteogenesis using external fixators has been done for many years, but the external fixator can be unwieldy and painful for the patient. It can also subject the patient to the risk of pin track infections, joint stiffness, loss of appetite, depression, cartilage damage and other side effects. An external fixator, e.g., around the patient/patient's limb, can also delay the beginning of rehabilitation.
In response to the shortcomings of external fixator distraction, intramedullary distraction nails which may be contained entirely within the bone have been surgically implanted. Some such nails may be automatically lengthened via repeated rotation of the patient's limb, which can sometimes be painful to the patient, and can often proceed in an uncontrolled fashion. This therefore makes it difficult to follow the strict daily or weekly lengthening regime that avoids nonunion (if too fast) or early consolidation (if too slow). Lower limb distraction rates are generally on the order of about one mm per day. Other intramedullary nails which have an implanted motor and may be remotely controlled by an antenna have also been developed. These devices are designed to be lengthened or distracted in a controlled manner, but, due to their complexity, may not be manufacturable as an affordable product. Others have proposed intramedullary distractors containing an implanted magnet, which allows the distraction to be driven electromagnetically by an external stator. Because of the complexity and size of the external stator, this technology has not been reduced to a simple and/or cost-effective device, which can be taken home to allow patients to do daily lengthenings. Non-invasively adjustable implantable distraction devices, at least one embodiment of which is magnetically non-invasively adjustable, have been developed and used clinically in both scoliosis and limb lengthening patients.
Knee osteoarthritis is a degenerative disease of the knee joint that affects a large number of patients, particularly over the age of 40. The prevalence of this disease has increased significantly over the last several decades, attributed partially, but not completely, to the rising age of the population as well as the increase in obesity. The increase may also be due to an increase in highly active people within the population. Knee osteoarthritis is caused mainly by long term stresses on the knee that degrade the cartilage covering the articulating surfaces of the bones in the knee joint. Oftentimes, the problem becomes worse after a particular trauma event, but it can also be a hereditary process. Symptoms include, but are not limited to, pain, stiffness, reduced range of motion, swelling, deformity, and muscle weakness. Osteoarthritis may include one or more of the three compartments of the knee: the medial compartment of the tibiofemoral joint, the lateral compartment of the tibiofemoral joint, and the patellofemoral joint. In severe cases, partial or total replacement of the knee is performed in order to replace the diseased portions with new weight bearing surfaces for the knee, typically made from implant grade plastics or metals. These operations may involve significant post-operative pain and require substantial physical therapy. The recovery period may last weeks or months. Several potential complications of this surgery exist, including deep venous thrombosis, loss of motion, infection, and bone fracture. After recovery, surgical patients who have received uni-compartmental or total knee replacement must significantly reduce their activity, removing running and high energy sports completely from their lifestyle.
For these reasons, surgeons are attempting to intervene early in order to delay or even preclude knee replacement surgery. Osteotomy surgeries may be performed on the femur or tibia, in order to change the angle between the femur and tibia, and thus adjust the stresses on the different portions of the knee joint. In closed wedge or closing wedge osteotomy, an angled wedge of bone is removed, and the remaining surfaces are fused together, creating a new improved bone angle. In open wedge osteotomy, a cut is made in the bone and the edges of the cut are opened, creating a new angle. Bone graft is often used to fill in the newly-opened, wedge-shaped space, and, often, a plate is attached to the bone with bone screws. Obtaining the correct angle during either of these types of osteotomy is almost always difficult, and, even if the final result is close to what was desired, there can be a subsequent loss of the correction angle. Some other complications associated with this technique include nonunion and material failure.
Amputation of the arm or the leg can result in a residual limb, with a stump, having a shortened bone (e.g., a shortened femur, tibia, fibula, humerus, radius or ulna). A prosthetic limb or prosthetic limb attachment which may be attached to a residual limb may have problems fitting or functioning when attached to a residual limb having insufficient bone length. There may be poor energy transfer between the residual limb and the attached prosthesis, as short lever arms generate less torque for a given force. This functional deficit is compounded when the lever arm is encased in very compliant tissue, such as a residual femur that is surrounded by the soft tissues of the thigh. This may further impair prosthesis control. Individuals having short residual limbs may display gait asymmetries and gait changes. The wearer of a prosthetic limb who has a relatively short residual limb may exhibit compensatory changes that affect posture and cause discomfort or injury to the spine or other body structures. Amputation may occur or may be performed for several reasons including war-related injuries, motor vehicle accidents, including motorcycle accidents, other types of trauma or cancer of the bone or other adjacent tissue.
In addition to the many different types of implantable distraction devices that are configured to be non-invasively adjusted, implantable non-invasively adjustable non-distraction devices have also been envisioned, for example, adjustable restriction devices for gastrointestinal disorders such as GERD, obesity, or sphincter laxity (such as in fecal incontinence), or other disorders such as sphincter laxity in urinary incontinence. These devices, too, may incorporate magnets to enable non-invasive adjustment.